Varying the process of rewriting to extend the life of a information carrier

ABSTRACT

The life of a rewritable information carrier such a CD-E covered by a phase-change recording layer is extended by varying the manner of representing information of an information block, for subsequent recordings, in the same portion of the record carrier. The manner can be changed, for example, by shifting the initial position at which representing information is written along the track over a distance randomly selected within predefined boundaries; or by writing a varying amount of information representing information from the end of the block before the start of information from the beginning of the information block to rotate the information in the track; or by scrambling the information in a varying manner such as using different keys. The manner of representation can be changed, for example, for each subsequent recording on the same portion of the record carrier. This causes different patterns to be recorded in the same portion, even if the same information is recorded in that portion of the track.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of application Ser. No. 08/800,633, filed Feb.14, 1997, now U.S. Pat. No. 6,115,340.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a device for recording an information carrierof a rewritable type, the information carrier comprising a track and thedevice comprising recording means for recording an information block ina part of the track from an initial position, the information blockrepresenting information in a predefined manner.

The invention further relates to a method of recording an informationcarrier of a rewritable type, the information carrier comprising atrack, and an information block being recorded in a part of the trackfrom an initial position, the information block representing informationin a predefined manner.

The invention also relates to an information carrier of a rewritabletype recorded in accordance with the method.

The invention also relates to a device for reading an informationcarrier of a rewritable type recorded in accordance with the method, thedevice comprising reading means for reading and decoding the informationblocks.

2. Description of the Related Art

Such an arrangement, method and information carrier are known from U.S.Pat. No. 5,388.105. The device disclosed therein is suitable for aninformation carrier of an optically rewritable and readable type, suchas, for example, a Compact Disc Erasable (CD-E), which has a rewritablelayer of phase-change material. Such information carrier has a preformedtrack, a so-called pregroove. The pregroove comprises addressinformation and is intended for positioning a write head during therecording process for recording in a track optically readable patternswhich represent information. The information is contained in blockswhich are recorded in specific parts of the track, so-called sectors,from an initial position depending on the address information. Theinformation is then represented in a certain manner by the opticallyreadable patterns which form the block. This representation includes,for example, a sector identification (ID), a synchronization zone, adata block and error detection and correction data, which information iscontained in the data block under a specific coding. A problem with theknown device is that the optically readable patterns start differingfrom the desired form when the information carrier is recordedrecurrently, so that the reading quality is degraded. This reduces theuseful life of an information carrier.

It is an object of the invention to provide a device in which thedeviations of the patterns are counteracted.

SUMMARY OF THE INVENTION

For this purpose, the device according to the invention is characterizedin that the recording means are arranged for substantially shifting theinitial position along the track over a randomly selected distancewithin predefined boundaries and/or for adapting the manner ofrepresentation. The invention is also based on the recognition that thedeviation of the patterns formed in recurrent recording strongly dependson the correlation between blocks recorded on the same part of thetrack, the recording of the same or very similar blocks considerablyaccelerating the pattern degradation. A small shift of the patterns,such as a few (2 to 3) times the longest written mark used therein wasexpected to be sufficient. Surprisingly however such a small shift, e.g.of around 32 channelbits, proved insufficient, while a substantialshift, e.g. of at least around 128 bits, was found to be effective.

For this purpose, a method according to the invention is characterizedin that the initial position is substantially shifted along the trackover a distance arbitrarily chosen within predefined boundaries and/orthe manner of representation is adapted.

An information carrier according to the invention is recorded inaccordance with said method.

A reading device according to the invention is characterized in that thereading means are arranged for reading the information blocks frompositions substantially shifted over a distance arbitrarily chosenwithin predefined boundaries. Also, or alternatively decoding theinformation blocks is carried out in accordance with the adapted mannerof representation of the information therein.

As a result of the aforesaid measures according to the invention,constantly varying patterns will be recorded on every part of the track,thus counteracting the accelerated degradation. An advantageous effectof this is the lengthening of the useful life of the informationcarrier. This advantageous effect particularly occurs when customaryfile management systems are used that rewrite file managementinformation always on the same parts of the track.

An embodiment for the device according to the invention is characterizedin that the manner of representation of the recorded information may berecovered from the information block itself when read out. This isadvantageous in that the recovery of the information from a readinformation block is independent of information about the manner ofrepresentation stored elsewhere.

A further embodiment for the device according to the invention ischaracterized in that the manner of representation of the recordedinformation comprises scrambling with a scramble key which scramble keyis included in the information block. This is advantageous in that anycorrelation between information blocks to be recorded on the samelocation is reduced with scrambling.

A further embodiment for the device according to the invention ischaracterized in that the manner of representation of the recordedinformation comprises including a variable amount of dummy data in theinformation block, which dummy data is recognizable when read out. Theadvantage of this is that by recurrently adding a variable amount ofdummy data, possibly similar patterns in an information block will berecorded each time at different positions. If the of dummy data is addedprior to the information in an information block, old information blockswill be largely overwritten and so invalid portions will not continue tobe readable.

A further embodiment for the device according to the invention ischaracterized in that the manner of representation of the recordedinformation comprises including a first variable amount of dummy databefore and a second variable amount of dummy data following theinformation in the block, while the sum of the first and second variableamount is substantially constant. The advantage of this is, that thetotal length of the information block will be substantially constant,allowing recording in a fixed location, while the information content isnevertheless recorded in randomly changing locations.

A further embodiment of the device according to the invention ischaracterized in that the mode of representation of the recordedinformation comprises rotating the information over a randomly selecteddistance in the information block. Information which extends beyond oneside of the information block is added to the other side. This isadvantageous in that no additional space on the disc is necessary forrotating the information. This is particularly advantageous whensynchronization patterns are supplied which shift along with theinformation and are therefore not always located in the same position.

A further embodiment of the device according to the invention ischaracterized in that the mode of representation of the recordedinformation comprises including the randomly selected distance in therespective information block. This is advantageous in that the distanceof the rotation of the information can then be simply derived. This isparticularly advantageous when synchronization patterns are used whichshift along with the information, because in that case the amount ofinformation before the first synchronization pattern and/or after thelast synchronization pattern can be determined when read out.

These and other aspects of the invention will be apparent from andelucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings 1 to 7:

FIG. 1 shows an information carrier of a writable type,

FIG. 2 shows a graph of the effect of recurrent recording versusshifting of the initial position,

FIG. 3 shows a device for recording and/or reading the informationcarrier,

FIG. 4 gives a diagrammatic representation of a part of the track inwhich information blocks are recorded,

FIG. 5 gives a diagrammatic representation of an adaptation procedure,

FIG. 6 gives a diagrammatic representation of information rotating in aninformation block and

FIG. 7 gives a diagrammatic representation of information blocksincluding variable amounts of dummy data. In the drawing FIGS., elementscorresponding to elements already described have like referencecharacters.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1a shows a disc-shaped information carrier 1 of a rewritable type.The information carrier includes a track 9 intended for recording, whichtrack is arranged in a helical pattern of windings. The windings mayalso be arranged concentrically in lieu of helically. The track 9 isindicated on the information carrier by a servo pattern in which, forexample, a pregroove 4 enables a read/write head to follow the track 9during the scanning operation. The servo pattern may also includes, forexample, regularly divided sub-patterns which periodically cause signalsto occur in a tracking servo. FIG. 1b shows a section along b—b of theinformation carrier 1, in which a substrate 5 is covered by a rewritablerecording layer 6 and a transparent layer 7. The pregroove 4 may also bearranged as a raised part or as a material property different from itssurroundings. The recording layer 6 may be recorded optically ormagneto-optically by a device for recording information blocks.Information on the information carrier is represented by patterns ofmarks. In the track 9, each mark being formed by one or more writepulses of a constant or variable write power which depends on, forexample, the length of the mark. The write parameters, such as the writepower, the number of pulses, the variation, the duty cycle etc. are tobe attuned to the information carrier, whose material properties play alarge role. An example of a writable information carrier is the CDerasable which is covered by a layer of phase-change material. Adescription of the reading of a CD and the use of a pregroove may befound in the title “Principles of Optical Disc Systems” by Bouwhuis etal., ISBN 0-85274785-3.

The FIGS. 1c and 1 d show two examples of a periodic modulation (wobble)of the pregroove. This wobble causes an extra signal to be developed inthe tracking servo pick-Lip. The wobble is, for example, frequencymodulated with an auxiliary signal which auxiliary signal containsencoded auxiliary information. The auxiliary information may be addressinformation indicating position in the longitudinal direction along thetrack. A description of an information carrier containing such auxiliaryinformation may be found in EP-0 397 238. The initial position in thetrack for writing information blocks may be derived from the addressinformation on this information carrier.

The invention is likewise applicable to information carriers on whichthe position along the track is determined differently, such as, forexample, via a separate reference pattern or via patterns previouslyrecorded on the information carrier. The invention may also be appliedto rewritable information carriers of another structure, such as, forexample, an optical tape. These information carriers may be providedwith address information in a different manner, for example, viainformation along an auxiliary track.

FIG. 2 shows a graph of the effect of recurrent recording versusshifting of the initial position. The graph represents the situation inwhich always the same information block is recurrently recorded on aspecific part of a rewritable information carrier. The information blockis formed by optically readable marks of different lengths, for whichthe length differences are always a multiple of a fixed distance, aso-called channel bit. The quality of the read signal is alwaysassessed, for example, on the basis of jitter or an eye pattern of theread signal. When recorded recurrently, the initial position of theinformation block in the longitudinal direction of the track is shiftedeach time over a random distance within specified boundaries. The numberalong the X-axis 31 denotes the distance between these boundaries inchannel bits. Along the Y-axis 32 (logarithmically) is shown the numberof times a specific part of a track has been recorded. A measuring pointis found by recording until a specific degradation of quality occurs. Inpulse position modulation (PPM) customary for known rewritable recordingsystems, only brief marks are recorded in a distributed manner. Howeverwhen pulse length modulation (PLM) is used, which makes a higherinformation density possible, long marks often occur. An example of PLMwith high information density is the EFM+ channel code described inPCT/IB95/00070, used in the high-density CD. Measurements have shownthat an intensified version of the phenomenon occurs, if the patternscomprise stretched out, contiguously recorded marks. Furthermore, thephenomenon appears to occur especially if the frequency spectrum of therunning average of the recorded patterns includes low-frequencycomponents. The invention is therefore eminently suitable for use incombination with PLM. The curve 33 running through the measured pointsreflects a relation between the number of times a recording is made andthe degree to which the recorded patterns are different each time theyare repeated. This relation has surprisingly shown that the usablenumber of times a rerecording can be made diminishes if the samepatterns are recurrently recorded on a (substantially) fixed position onthe information carrier. Furthermore, a considerable shift of theinitial position is necessary for attaining the maximum attainableuseful life. Contrary to expectations a small shift of around 32channelbits (first measurement value 34) did show a rather low number ofusable rewrites. Such a shift, which is a few times the longest usedmark in PLM, would distribute such long marks well beyond overlapping.In a practical example in CD-E having patterns of 17 channel bits forone information byte the longest mark is 11 channel bits. A shift of 2information bytes, i.e. 34 channelbits, was expected to be sufficient.However only at a substantially larger shift of around 100 bits (secondmeasurement value 35 at 128 bits) a considerable improvement was found.Beyond a shift of the order of 1000 channel bits (fifth measurementvalue 36) no further improvement was found for the measured informationcarrier.

FIG. 3 shows a device according to the invention for reading and/orrecording the disc-shaped information carrier. The device comprisescoding means 52 and a read/write unit 57 for writing and/or readinginformation blocks on the information carrier 1. Information is appliedto input 51 and converted into a write signal in coding means 52, theinformation being represented in the information blocks in a predefinedmanner. The write signal is applied to the read/write unit 57. Theinformation carrier I rotates, driven by drive means 58. The read/writeunit 57 scans via beam 56 the track 9 and writes patterns of marks in itwhich represent the information. During the scanning operation, theread/write unit 57 is positioned over track 9 by a servo system of acustomary type (not shown). The system controller 59 controls thescanning of the information carrier 1 via the drive means 58 and theservo system. Generally, such a device will also comprise decoding means53 for recovering the information from the patterns read out via thereadiwrite unit 57. The recovered information is then produced on theoutput 54. A device for recording only may not include the decodingmeans 53 and output 54, while a device for reading only may not includethe coding means 52 and input 51. The device further may includedemodulator means 55 for recovering the address information. The servosignals generated while the track is being scanned, are applied to thedemodulator means 55 which is arranged for demodulating the servosignals for recovering the auxiliary signal. The demodulator means 55derives the address information from the auxiliary signal whichinformation is passed on to the system controller 59.

According to the invention, the write means 52, 57, 59 are arranged forwriting the information blocks in such a way that writing of the samepatterns at the same position in a specific area of the track isminimized. A first measure to prevent this end is that the systemcontroller 59 shifts the initial position of an information block to berecorded always by a random distance relative to the nominally definedinitial position. This distance is chosen at will, but does lie withinpredefined boundaries, because otherwise it would be possible forpreceding or succeeding information blocks in the track to be partlyoverwritten. Furthermore, it will be a large distance compared topattern distances found in channel coding. With the respectiverewritable information carrier, ample room should be left open betweenthe blocks to make such a shift in position possible. This may berealized, for example, by reserving ample space for an information blockand the maximum (peak-to-peak) shift between the nominal initialpositions, for example, laid down in a standard system-specification. Ashift by 1,000 bits may be taken as an example, which leads to a loss ofinformation density of about 3% for the EFM+ code (8/16 data/channelbits) and a 2 kbyte information block and ID synchronization zones etc.and about 0.2% for a 32 kbyte information block. The effect of the firstmeasure is further shown in FIG. 4.

A second measure according to the invention is the constant adaptationof the manner of representation of the information in the informationblocks. For this purpose, the coding means 52 is arranged to provide aselected adaptation which is always different. A key which is indicativeof the mode of representation, and which is therefore necessary fordecoding the information block again when read Out, is generated by thesystem controller 59. For example, a random byte creating 256 differentkeys may be used as a key. Alternatively, it is possible to useconsecutive keys. They may then also function as a repetition counter,which shows by the key how often a part of the track has already beenrecorded. When a certain maximum is reached, that particular part of thetrack may then be blocked from further use, before errors will developduring reading. For generating the consecutive keys, a system may beused in which a large part of the bits between the consecutive keys isdifferent. The key is stored either in the information block orsomewhere else on the information carrier, for example, in a centralregion. In this respect it is important for the key to have maximumprotection against errors during reading, since the information is nolonger recoverable in the event of an incorrect key. For this purpose,the key may be protected by the customary error-correcting codes, butmay also be repeated at several points in the information block. It isalternatively possible for the keys to be stored in a memory (forexample, in the system controller) in the device. The memory may be apermanent memory; the information carrier can then only be read by therespective device. Alternatively, it is possible for the contents of thememory to be recorded on the information carrier at specific instants.

For adapting the manner of representation of the recorded information,scrambling may be used, for example. For such an adaptation, the writesignal is processed in known fashion with a bit stream (for example, byan EX-OR operation). For generating the bit stream, use is made of agenerator circuit in which the generated bit stream depends on the key.This key may be included in the information block, for example, in theID. It is attractive for the ID to be recoverable in a simple mannerfrom the read signal, since the ID should to be known rapidly to thesystem controller when a desired information block to be jumped to. Forthis purpose, a simpler scrambling operation may be used for the ID.So-called self-synchronizing scramble operations may also be used forscrambling. This does not require any explicit key, but the descramblerwill again be in line after a specific number of bits of a scrambledsignal have been processed. It should be observed that when informationis scrambled whose key is not changed for each writing operation, but isderived, for example, in information from the ID, the desired usefuleffect will not be achieved.

A further measure for adapting the manner of representation of therecorded information is the addition of an amount of dummy data to theinformation block, for example, by including a variable length zonefilled with a randomly selected, but fixed dummy byte for each recordingat the beginning of an information block. After this dummy zone thenfollows the ID zone which can be recognized in a fixed manner. As aresult, the ID zone will always be found during the reading of theinformation block and still the whole track zone is recorded, so that noold or no longer valid parts of previously recorded information blockscontinue to be present. Alternatively, at the end of the informationblock, such a zone with variable dummy data can be added while thelength of the zone to be recorded (dummy zone+block contents+dummy zone)may then be constant. The manner of representation then comprisesincluding a first variable amount of dummy data before and a secondvariable amount of dummy data following the information of the block,while the sum of the first and second variable amount is substantiallyconstant.

FIG. 7 schematically shows three possible situations between successiveinformation blocks having dummy data included therein as describedabove. In the upper situation a first block 71 and a second block 72 areshown having a nominal (longitudinal) position of the informationcontents. When recorded in the track the blocks would be alignedlaterally and therefore overlapping in a small margin 80. Theoverlapping area has the advantage, that the track will be recordedcontinuously also in the event of small positioning inaccuracies causedby actual timing errors. In a track uninterrupted recording marksprevent disturbance of servo systems and signal processing. Theinformation content of the first block 71 ends with a synchronizationmark 73, as indicated by the thick line. After this synchronization mark73 an end link area 78 comprising dummy data follows until the physicalend of recording 74. The second block 72 starts from a physical startingpoint 75 with start link area 79 comprising dummy data, followed by asynchronization mark 77 and the information contents of the secondblock. The area between the last synchronization mark 73 of the firstblock and the first synchronization mark 77 of the second block isusually called a linking frame. Further linking frames may be present inthe second block before the information contents to enable the signalprocessing of a reading device to adjust to the new block, which mayhave been recorded using slightly different parameters. Thesynchronization marks preceding linking frames may have a special valueindicating a linking frame. The linking frame between two successiveinformation blocks has a nominal length 76, including the overlappingmargin 80. In the middle situation two further successive blocks 81, 82are shown having a shifted position of the information contents. Thefirst block 81 has a large amount of dummy data at the beginning (notshown) and a complementary small amount 84 of dummy data at the end,resulting in the total length and the ending point of the first block 81being equal to the upper situation, while the actual informationcontents have been shifted a distance+Δ. The second block 82 in themiddle situation has a minimal amount of dummy data at the beginning, sothe linking frame 83 has the shortest possible length, while theinformation contents of the second block is shifted a distance−Δ. Thelower situation shows a first block 85 having a shift of−Δ and thereforea large amount of dummy data at the end. The second block 86 here has ashift of+Δ, resulting in a maximum linking frame 87. The maximum shiftshould be sufficiently large as described above. In a practical examplethe frames between synchronization marks could be 91 bytes, one bytebeing represented by 16 channel bits as in EFM+ (see above). A shift of62 bytes (992 bits) would result in a Δ of maximum 31. The end link area78 of a linking frame is 49 bytes, while the start link area 79 is 50bytes, and an overlapping area of 8 bytes allowing a jitter in thepositioning of 4 bytes of both information blocks. This results in thelower situation in a maximum end link area of 49+31=80 bytes and amaximum start link area of 50+31=81 bytes and therefore in a maximumlinking frame 87 of 80+81−8=153 bytes, which equals the nominal lengthaugmented by the total shift 91+62=153. Correspondingly in the middlesituation a minimum end link area of 49−31=18 bytes and a minimum startlink area of 50−31=19 bytes result in a minimum linking frame 83 of19+18−8=91−62=29 bytes. These limits of 153 and 29 bytes are the worstcase situations in the above circumstances. It has to be noted, that oneor more linking frames will be necessary in a practical system anywayfor allowing the servo and signal processing electronics to adjust tothe following information block, which very well may be written underdifferent conditions in a different recorder from the previous block. Sothese frames can be useful for preparing reading or recording in adevice. Applying the substantial shift according to the invention byadding dummy data as described here in combination with linking framesdoes not require any additional disk space, and so advantageously allowsa high information density without loss of storage capacity.

The aforesaid two different measures may be implemented separately or incombination. An advantage of exclusively applying shift is that areading device may not need to have specific measures for reading arewritable information carrier recorded in accordance with theinvention. For that matter, reading is then substantially the same asreading a Read-Only or Write-Once information carrier. This is anadvantage for computer and multimedia applications in which informationcarriers of different types are used. If relatively small informationblocks are recorded, the shifting may considerably change theinformation density. In that case it is attractive, for example, tocombine a limited shift with a scrambling operation. The scramblingstrongly reduces the autocorrelation of the information block to berecorded. Depending on the selected channel code, certain patterns maycontinue to be fixed, for example, such as synchronization patterns inthe EFM+ channel code. A limited shift operation will then be sufficientto record these patterns always at a different position on the track. Byselecting a limited shift, it is naturally possible to achieve a higherinformation density on the information carrier.

According to the invention, the read means including the read/write unit57 and the decoding means 53 as shown in FIG. 3 are arranged for readingthe information blocks from positions substantially shifted over adistance arbitrarily chosen within predefined boundaries and/or fordecoding the information blocks in accordance with the adapted manner ofrepresentation. The measures as described above for adapting the mannerof representation are implemented in a complementary way in the decodingmeans, while the substantially shifted position and/or linking frames asdescribed with FIG. 7 are handled by the read/write unit in combinationwith the servo system and the decoding means 53.

FIG. 4 gives a diagrammatic representation (and not to scale) of a trackin which information blocks are recorded on shifted initial positions.The nominal initial positions are denoted by the dashed lines 41, 42 and43. They are fixed mutual distances 40 apart. Furthermore, the system ofshifting may also be applied to a subdivision of the track withdifferent spacings between the nominal initial positions. The recordedinformation blocks are referenced 44, 45 and 46. There may be noticedthat the first block 44 commences at the nominal initial position, thesecond block 45 at a specific distance after the nominal initialposition and the third block 46 before the nominal initial position. Thespacing between the blocks is therefore variable. After severalrecordings, the spacing will partly contain old information as is shownat the start of the last block 47. However, there should be observedthat in known recording systems for writable information carriers somemargin is given between the blocks for a variation of the initialposition of an information block. This margin (for example, 16 bits) maybe used to compensate for mechanical and electrical tolerances in theinitial position, which occur when the recording operation is started.It has been found that such a margin is not sufficient to effectivelycounteract detoriation, as described with FIG. 2.

FIG. 5 gives a diagrammatic representation of an adaptation procedure.Two measures are combined for this purpose, scrambling and shifting. Thesystem controller 59 carries out the following steps:

S1: the system controller receives the order for recording aninformation block and determines a nominal initial position.

S2: the system controller generates a random key and supplies same tothe coding means 52 and orders the coding means to scramble with thiskey. The key itself, for example, is also included in the block.

S3: the system controller adds a random distance to the nominal initialposition.

S4: the system controller positions the read/write unit 57 over thedesired zone of the track 9 and waits for the computed initial positionto be located under the read/write unit, for example in dependence ofthe address information read by the demodulator means 55.

S5: the system controller orders the write means 52, 57 to write. Thereading operation (not shown) is carried out in similar manner, in whichthe key is first recovered from the read signal and applied to thedescrambler means in the decoding means 53. Subsequently, the decodingis carried out as in known reading devices.

FIG. 6 gives a diagrammatic representation of rotating information in aninformation block. In a first information block 61 the information isplaced in the nominal position. As is customary, the information block61 starts with a RUN-IN part 63 which includes a run-in pattern for thereading means to run in, more particularly, for a Phase Locked Loop(PLL) to lock on to the regeneration of the data clock, and theinformation block is closed by a GUARD part 67 for avoiding an abrupttransition to an unrecorded part of the information carrier or patternsrecorded previously. Between RUN-IN 63 and GUARD 67 there is located aninformation area 60 containing one or more data blocks Dn andsynchronization patterns S; in FIG. 6 are shown 4 data blocks DO (65),D1, D2 and D3 (66) and each data block is preceded by a synchronizationpattern 64. To avoid data blocks and synchronization patterns S alwaysbeing recorded in the same position when recorded recurrently, theinformation in the information area 60 is rotated by a random distance aeach time it is recorded, as is shown in the second information block 62in FIG. 6. Rotation, alternatively referenced wrap-around, is meant tobe understood as the shifting of all the bits in the information area 60in a particular direction, for which the bits that are shifted over theboundary of the data area are shifted to the vacant space on the otherboundary of the information area. In the example of the informationblock shown 62, the data blocks and synchronization patterns are shiftedover a channel bits and the information of the last data block D3 issplit up into two parts 68, 69. The second part 69 of the last datablock D3 would end up past the terminal boundary 70 after the shift andis added to the first data block after the initial boundary of theinformation area 60. Needless to observe that the rotation can also beeffected in the other direction, while particularly D0 is split up intotwo parts. During the reading operation, the shift a is to be derivedfrom the read signal, and the beginning and/or end of the informationarea 60 are to be derived too. This may be effected, for example, bychoosing a specific format for the RUN-IN patterns and/or the GUARDpatterns. Also the value of a can be explicitly included in theinformation block, preferably in a predefined position relative to thesynchronization patterns. Preferably a variable pattern is used for theRUN-IN and/or GUARD part of the information block, because otherwise thequality of these parts will degrade faster than the parts of the datablocks. For example, by using the (variable) value of a in the RUN-INpattern, the RUN-IN is variable and a can be recovered when read out.Alternatively, it is possible to vary only the position of thesynchronization patterns by a and scramble the remaining data with ascramble key which is then included, for example, in the RUN-IN part.For reading blocks that display shifted synchronization patterns, thereading device preferably comprises a memory for storing the signal thatprecedes the first synchronization pattern, the contents of the memorybeing decoded after synchronization has been established. In the secondinformation block 62 shown, the decoding may, for example, be effected,from the memory that stores the part 69 of the block which part is addedto the first data block, subsequent to the decoding of the first part 68of the last data block D3.

By selecting the distance a sufficiently large (of the order of 1000channel bits, cf. FIG. 2), there is achieved that the rewritability forinformation blocks with synchronization patterns is high. This obviouslyholds likewise for information blocks without fixed synchronizationpatterns for which the synchronization of the decoding is effecteddifferently when read out. It is also possible to use information blockswithout a RUN-IN or GUARD area, for example, if a plurality ofinformation blocks are recorded continuously. In all cases there is theadvantage that rotation in this fashion does not ask for additionalspace between the information blocks, because they can always berecorded in the same positions.

What is claimed is:
 1. A device for recording information in tracks of arewritable information carrier, comprising: means for determining aportion of a track for recording a representation of a block ofinformation received by the recording device, the track portion having abeginning and an end; means for recording information in the trackportion with a particular manner of representation, the recordedinformation including the representation; life extending means forvarying the manner of representation for subsequently recordedrepresentations in the same track portion so that during subsequentrecording the same information in a subsequent representation as in aprevious representation would be recorded with a varied manner ofrepresentation resulting in different recorded information at least in apart of the same track portion extending more than 32 bits; wherein, themanner of representation includes an initial position in the trackportion at which each representation begins; and varying the manner ofrepresentation includes shifting the initial position of a subsequentrepresentation by a predetermined amount, with respect to the beginningof the track portion, of more than 32 bit lengths with respect to theinitial position of a previous representation in the same track portion.2. The device of claim 1 in which he shifting of the initial positionoccurs by a predetermined random or pseudo random amount for eachsubsequent recording.
 3. A device for recording information in tracks ofa rewritable information carrier, comprising: means for determining aportion of a track for recording a representation of a block ofinformation received by the recording device, the track portion having abeginning and an end, the representation including beginning informationrepresenting information at the beginning of the information block andending information representing information at the ending of theinformation block; means for recording information in the track portionwith a particular manner of representation, including therepresentation; life extending means for varying the manner ofrepresentation for subsequently recorded representations in the sametrack portion so that during subsequent recording the same informationin a subsequent representation as in a previous representation would berecorded with a varied manner of representation resulting in differentrecorded information at least in a part of the same track portionextending more than 32 bits; wherein, the manner of representationincludes a starting position at which beginning information begins to berecorded in the track; and varying the manner of representation includesshifting the starting position of a subsequent representation by apredetermined amount, with respect to the beginning of the trackportion, of more than 32 bit lengths with respect to the startingposition of a previous representation in the same track portion.
 4. Adevice for recording information in tracks of a rewritable informationcarrier, comprising: means for determining a portion of a track forrecording a representation of a block of information received by therecording device, the track portion having a beginning and an end, therepresentation including beginning information representing informationat the beginning of the information block and ending informationrepresenting information at the ending of the information block; meansfor recording information in the track portion with a particular mannerof representation, the recorded information including therepresentation; life extending means for varying the manner ofrepresentation for subsequently recorded representations in the sametrack portion so that during subsequent recording the same informationin a subsequent representation as in a previous representation would berecorded with a varied manner of representation resulting in differentrecorded information at least in a part of the same track portionextending more than 32 bits; wherein, the manner of representationincludes a starting position in the track at which beginning informationstarts to be recorded in the track portion; and varying the manner ofrepresentation includes moving, in a subsequent representation, apredetermined amount of more than 32 bit lengths, of ending informationto a position prior to the starting position with respect the startingposition of a previous representation in the same track portion.
 5. Thedevice of claim 4 in which: the manner of representation includes aninitial position in the track portion at which the recorded informationrepresenting the information of the block begins in the track portion;and varying the manner of representation further includes shifting thestarting position of the recorded information with respect to theinitial position for the subsequent recordings in the track portion, andfilling the space between the initial position and the beginningposition with ending information so that the ending information rotateswith respect to the track during subsequent recordings, the shift beingwithin a range of more than 32 bit lengths so that, the initial positionshifts with respect to the initial portion by at times more than 32 bitlengths with respect to the initial position of a previous recording inthe track portion.
 6. The device of claim 4 in which the amount ofending information moved varies by a random or pseudo random amount foreach subsequent recording.
 7. The device of claim 1 in which: therepresentation includes dummy data; and varying the manner ofrepresentation further includes varying the amount of dummy data in asubsequent representation by an amount of more than 32 bit lengths withrespect to the dummy data of a previous representation.
 8. A device forrecording information in tracks of a rewritable information carrier,comprising: means for determining a portion of a track for recording arepresentation of a block of information received by the recordingdevice, the track portion having a beginning and an end; means forrecording information in the track portion with a particular manner ofrepresentation, including the representation; life extending means forvarying the manner of representation for subsequently recordedrepresentations in the same track portion so that during subsequentrecording the same information in a subsequent representation as in aprevious representation would be recorded with a varied manner ofrepresentation resulting in different recorded information at least in apart of the same track portion extending more than 32 bits; wherein themanner of representation includes recording dummy data in the trackportion in a position subsequent to the representation; and varying themanner of representation includes varying the amount of dummy datawritten prior to a subsequent representation from the amount of dummydata written prior to a previous representation by an amount of morethan 32 bit lengths.
 9. A device for recording information in tracks ofa rewritable information carrier, comprising: means for determining aportion of a track for recording a representation of a block ofinformation received by the recording device, the track portion having abeginning and an end; means for recording information in the trackportion with a particular manner of representation, the recordedinformation including the representation and the manner ofrepresentation including recording dummy data in the track portion priorto the representation; life extending means for varying the manner ofrepresentation for subsequently recorded representations in the sametrack portion so that during subsequent recording the same informationin a subsequent representation as in a previous representation would berecorded with a varied manner of representation; and wherein, varying ofthe manner of representation includes varying the amount of dummy datain positioned prior to a subsequent representation by an amount of morethan 32 bit lengths with respect the dummy data of a previousrepresentation.
 10. Apparatus for programming a rewritable informationcarrier, comprising: means for providing programmed apparatus fordetermining a portion of a track for recording a representation of ablock of information received by the recording device, the track portionhaving a beginning and an end; means for providing programmed apparatusfor recording information in the track portion with a particular mannerof representation, the recorded information including therepresentation; means for providing programmed apparatus for extendingthe life of the record carrier by varying the manner of representationfor subsequently recorded representations in the same track portion sothat during subsequent recording the same information in a subsequentrepresentations as in previous representations would be recorded with avaried manner of representation resulting in different recordedinformation at least in a part of the same track portion extending morethan 32 bits; wherein, the manner of representation includes an initialposition in the track portion at which each representation begins; andvarying the manner of representation includes shifting the initialposition of a subsequent representation by a predetermined amount, withrespect to the beginning of the track portion, of more than 32 bitlengths with respect to the initial position of a previousrepresentation in the same track portion.
 11. A method for producing adevice for recording information in tracks of a rewritable informationcarrier, comprising: providing means for determining a portion of atrack for recording a representation of a block of information receivedby the recording device, the track portion having a beginning and anend; providing means for recording information in the track portion witha particular manner of representation, the recorded informationincluding the representation; providing means for extending the life ofthe record carrier by varying the manner of representation forsubsequently recorded representations in the same track portion so thatduring subsequent recording the same information in a subsequentrepresentation as in a previous representation would be recorded with avaried manner of representation resulting in different recordedinformation at least in a part of the same track portion extending morethan 32 bits; wherein, the manner of representation includes an initialposition in the track portion at which each representation begins; andvarying the manner of representation includes shifting the initialposition of a subsequent representation by a predetermined amount, withrespect to the beginning of the track portion, of more than 32 bitlengths with respect to the initial position of a previousrepresentation in the same track portion.
 12. The apparatus of claim 10in which the apparatus consists essentially of programmed computer mediawhich can be used for programming to produce the device.
 13. The deviceof claim 1 in which: the manner of representation varies by a random orpseudo random amount for subsequent recording in the track portion; theshifting of the initial position occurs by a random or pseudo randomamount for each subsequent recording; the manner of representationincludes a starting position at which information representinginformation at the beginning of the information block is recorded in thetrack; and varying the manner of representation includes shifting thestarting position, of the recorded information representing theinformation at the beginning of the block, with respect to the beginningof the track portion; the shifting of the starting position occurs by arandom or pseudo random amount for each subsequent recording; the mannerof representation can be determined from the recorded information whenit is subsequently read out of the track portion; varying the manner ofrepresentation includes varying an amount of ending information,representing information at the end of the information block, recordedprior in position to the starting position so that the informationrepresenting subsequent information blocks rotates, within the trackportion, with respect to the beginning of the track portion, forsubsequent recordings in the track portion; the manner of representationincludes scrambling the information block and varying the manner ofrepresentation includes varying the method of scrambling the informationfor such subsequent recording, two or more methods of scrambling theinformation being used for different subsequent recordings; varying themanner of representation includes varying an amount of dummy datarecorded prior in position to the representing information in the trackportion; varying the manner of representation includes varying an amountof dummy data recorded subsequent in position to the representinginformation in the track portion; the scrambling is performed using ascrambling key and varying the manner of representation includes varyingthe scramble key; and the total amount of prior and subsequentlypositioned dummy data does not vary as the manner of representationvaries.
 14. The device of claim 9 in which: the manner of representationvaries by a random or pseudo random amount for subsequent recording inthe track portion; the manner of representation includes an initialposition at which the recorded information representing the informationof the block begins in the track portion; and varying the manner ofrepresentation includes shifting the initial position of therepresenting information with respect to the beginning of the trackportion so that the information representing subsequent informationblocks shifts with respect to the beginning of the track portion forsubsequent recordings in the track portion; the shifting of the initialposition occurs by a random or pseudo random amount for each subsequentrecording; the manner of representation includes a starting position atwhich information representing information at the be ginning of theinformation block is recorded in the track ; and varying the manner ofrepresentation includes shifting the starting position, of the recordedinformation representing the information at the beginning of the block,with respect to the beginning of the track portion; the shifting of thestarting position occurs by a random or pseudo random amount for eachsubsequent recording; the manner or representation varies at least in apart of the track portion extending more than 32 bits; the manner ofrepresentation can be determined from the recorded information when itis subsequently read out of the track portion; varying the manner ofrepresentation includes varying an amount of ending information,representing information at the end of the information block, recordedprior in position to the starting position so that the informationrepresenting subsequent information blocks rotates, within the trackportion, with respect to the begining of the track portion, forsubsequent recordings in the track portion; the manner of representationincludes scrambling the information block and varying the manner ofrepresentation includes varying the method of scrambling the informationfor such subsequent recording, two or more methods of scrambling theinformation being used for different subsequent recordings; varying themanner of representation includes varying an amount of dummy datarecorded subsequent in position to the representing information in thetrack portion; the scrambling is perfomed using a scrambling key andvarying the manner of representation includes varying the scramble key;and the total amount of prior and subsequently positioned dummy datadoes not vary as the manner of representation varies.
 15. The method ofclaim 11 in which: the manner of representation varies by a random orpseudo random amount for subsequent recording in the track portion; theshifting of the initial position occurs by a random or pseudo randomamount for each subsequent recording; the manner of representationincludes a starting position at which information representinginformation at the beginning of the information block is recorded in thetrack; and varying the manner of representation includes shifting thestarting position, of the recorded information representing theinformation at the beginning of the block, with respect to the beginningof the track portion; the shifting of the starting position occurs by arandom or pseudo random amount for each subsequent recording; the mannerof representation can be determined from the recorded information whenit is subsequently read out of the track portion; varying the manner ofrepresentation includes varying an amount of ending information,representing information at the end of the information block, recordedprior in position to the starting position so that the informationrepresenting subsequent information blocks rotates, within the trackportion, with respect to the beginning of the track portion, forsubsequent recordings in the track portion; the manner of representationincludes scrambling the information block and varying the manner ofrepresentation includes varying the method of scrambling the informationfor such subsequent recording, two or more methods of scrambling theinformation being used for different subsequent recordings; varying themanner of representation includes varying an amount of dummy datarecorded prior in position to the representing information in the trackportion; varying the manner of representation includes varying an amountof dummy data recorded subsequent in position to the representinginformation in the track portion; the scrambling is performed using ascrambling key and varying the manner of representation includes varyingthe scramble key; and the total amount of prior and subsequentlypositioned dummy data does not vary as the manner of representationvaries.
 16. The device of claim 9 in which the dummy data fills thespace between the beginning of the track portion and a beginningposition of the recorded information for each subsequent recording sothat all of the previous recordings before the beginning portion areoverwritten each time.
 17. The device of claim 9 in which the amount ofdummy data recorded prior to a subsequent representation relative theamount of dummy data recorded prior to a previous representation isincreased at some times and is decreased at other times.
 18. A devicefor reading information from tracks of a rewritable information carrier,comprising: means for determining a portion of a track for reading arepresentation of a block of information received by the recordingdevice, the track portion having a beginning and an end; means forreading information from the track portion, the information having aparticular manner of representation, the information so read includingthe representation; and the manner of representation including aninitial position in the track portion at which the representationbegins, the initial position of subsequently written representationsrelative to the initial position of previously written representationsvarying by a random or pseudo random amount of more than 32 bit lengthswith respect to the beginning of the track portion.
 19. The device ofclaim 4 in which: the manner of representation includes asynchronization signal recorded between the ending information and thestarting position in the track portion; and the position of thesynchronization signal varies depending on the variation of the positionof the starting position in subsequent recordings.